In certain wireless communication systems, multiple devices share access to the wireless communication medium, e.g., radio frequency (RF) channel or channels. Numerous communication protocols have been developed to control how devices access the medium. One technique that is common among many communication protocols is to detect the presence of a transmission from another communication device before a device initiates its own transmission on the medium. Transmissions are formatted as packets or frames, where an initial portion of the packet or frame comprises a start-of-packet pattern often referred to as a preamble. The data or payload of the packet follows the preamble.
It is common practice to configure communication devices to detect a packet or frame associated with a transmission on the communication channel by identifying the preamble associated with the packet. For example, received signal strength indicators, changes in energy, and auto- and cross-correlation functions are examples of techniques to detect a preamble. However it is not always possible for a device to observe the preamble (e.g., due to a collision of one or more packets or shutting down during a power save mode), and in fact the first observation that a communication device makes may comprise portions of a packet or frame that follow the preamble (e.g., data symbol) in which case the ability to detect a preamble alone is not a sufficient packet detection technique. In many cases, a communication device fails to see the transmission of a packet in the absence of detecting the preamble, except when an energy detection threshold is set to a relatively low value, in which case, false positive packet detections may occur.
A technique that allows a communication device to detect an in-progress packet without requiring detection of a start-of-packet pattern, e.g., a preamble, would be very helpful in improving performance of communication devices and the systems or networks in which the communication devices operate.